Senna pallida var. palmeri

  • Title

    Senna pallida var. palmeri

  • Authors

    Howard S. Irwin, Rupert C. Barneby

  • Scientific Name

    Senna pallida var. palmeri (Britton) H.S.Irwin & Barneby

  • Description

    177e. Senna pallida (Vahl) var. palmeri (Britton & Rose) Irwin & Barneby, stat. nov. Peiranisia palmeri Britton ex Britton & Rose, N. Amer. Fl. 23(4): 261. 1930.-"Vicinity of Acapulco, Guerrero, October 1894 to March 1895, E. Palmer 260."-Holotypus, US! isotypi, F (2 sheets), NY = NY Neg. 9396, US (2 sheets)!-Non Cassia palmeri Wats., 1887.

    Arborescent shrubs 1-5(-8) m, with terete whitish annotinous and virgate, deeply sulcate hornotinous branchlets, thinly strigulose distally but the lfts glabrous, of firm texture and subglaucescent, the 2-fld racemes at first axillary to coeval lvs, ultimately corymbose-paniculate and ± exserted.

    Stipules linear-setiform 2-6 x 0.2-0.3 mm.

    Major lvs 5.5-12(-61) cm; petiole 16-40 mm, ±2-3 times as long as first segment of rachis; rachis (2-)2.5-8(-10) cm bluntly carinate dorsally; gland between proximal pair stipitate 1.4-2.8 mm, the body 0.5-1 mm wide; lfts 4-8(-9) pairs, the distal pair narrowly or broadly obovate obtuse or deltately subacute 15-25(- 30) x 7-12(-15) mm, 1.7-2.3 times as long as wide, simply pennmerved, the 5- 6 pairs of camptodrome secondary veins above fully immersed or almost so, beneath finely prominulous or merely discolored, subsequent venulation invisible.

    Peduncles 1.2-2.8 cm; pedicels 1.6-2.7 cm; long sepals 6.5-9.5 mm; long petals 2.4-3.1 cm; androecium glabrous, the filaments free, those of 4 median stamens 1.3-1.8 mm, of 3 abaxial ones 3.5-5 mm; anthers of 4 median stamens (as var. pallida) 4-6 mm, of 3 abaxial ones 5-7 mm, the beak (1.8-)2.2-3.5 mm.

    Stipe of pod 6-9 mm, the body 7-13(-15) x 0.65-0.8(-0.9) cm, the valves shallowly convex over seeds; seeds 3.1-3.7 x 1.8-3.1 mm, the areole 0.8-0.9 x 0.55-0.7 mm.-Collections: 9.

    Brushy flats and hillsides, from near sea-level behind the beach up to 800 m in the foothills, apparently local along the Pacific slope of Sa. Madre del Sur in Michoacan (n. of Playa Azul) and Guerrero (between rios Tecpan and Papagayo), and inland, in the hill-country w. of Iguala, Guerrero.-Fl. I-IV.

    The var. palmeri is in some ways intermediate morphologically between sympatric lowland var. pallida and allopatric upland var. quiedondilla, combining the relatively few pairs of leaflets of the former with the deeply sulcate young branchlets, the simply venulose leaflets, the corymbose-paniculate inflorescence and the broad pod of the latter. Although the pod is much wider (6.5-9 not 2.5-5 mm) than that of var. pallida, the seeds are not or scarcely larger and bear on the faces the same small areole. The strong resemblance in most technical features between var. palmeri and the Peruvian var. nemorosa, which has seeds of a size to match their pod, is no doubt due to convergent evolution.